Table of Contents
These curious little fishes are related to the sculpins anatomically, though their general appearance gives no hint of the fact. Their most striking external feature is that the body is armed with several rows of overlapping plates. The only Gulf of Maine species somewhat suggests a pipefish in this and in its slender form, but there is no danger of confusing one with a pipefish, for its mouth is of the ordinary form; and it has ventral fins. Some agonids have a spiny dorsal fin which others lack, while the ventral fins are situated far forward (only a little rearward of the pectorals) in all of them. Twenty-six of the many species included in the family are known from the western coast of North America from Bering Sea to southern California; two are known from the eastern coast of North America.
One of the eastern American species (Leptagonus decagonus, Bloch and Schneider 1801), with two dorsal fins, is Arctic, ranging southward only to northern Nova Scotia; the other, with only one dorsal fin (Aspidophoroides monopterygius) is a regular member of the Gulf of Maine fish fauna (p. 457).
 Some recent authors separate the group into two families, Agonidae or Sea Poachers for those with two dorsal fins, Aspidophoroididae or Alligatorfishes for those with only one dorsal fin. But it seems preferable, for the purposes of the present volume, to follow the older custom of uniting them in the one family Agonidae.
 A young specimen has been reported from Banquereau Bank (Rept. Newfoundland Fish. Res. Comm., vol. 2, No. 1, 1933, p. 127) as Agonus decagonus.